Air pressure responsive control for internal-combustion heaters



'o pia 1948..

Filed Doc. 13,

I w. A. MARSHALL, JR. s-rm. AIR PRESSURE RESPONSIVE CONTROL FOR 7INTlRNAL-COHBU$ TION HEATERS 5 Shuts-She 1 19 1948- w.'A. MARSHALL, JR..:rm. 3 5 AIR PRESSURE RESPONSIVE CONTROL FOR INTERNAL-COMBUSTION HEATERSFildd Dec. 13.19.43 -5 sheets-sheet:

' ,dmeh/ '5 Oct. 19 1948, w. A. MARSHALL, JR.. Em. 2,451,625

I AIR PRESSURE RESPONSIVB CONTROL FOR INTERNAL-COMBUSTION HEAT RS Fi ledDec." 13, 1943 s Sheets-Shut s Oct. 19- 1948- w. AMARSHALL. JR.. ETALi2,451,625

'- AIR PRESSURE RBSPORSIVE CONTROL FOR INTBRNAL-COIBUSTION HEATERS 5E113, 1 5 Sheets-Sheet4 -Qct.'19 1948- w.A. MARSHALLJR, ETAL 2,451,625

AIR PRESSURE RESPONSIVE CONTROL FOR INTERNAL-COMBUSTION HEATERS FiledDec. 13, 194; I 5 Shets-Shaat 5 Patented ct. 19, i9

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AI PRESSURE RESEONSE'E CGNTROL FOE KNTERNAL-COMEUSTIQN HIEETERSliilliam' A. Marshall, Jilin, Chicago, and John H.

Leslie, ll, Winnetka, ilk, assignors to Stewart- Warner Corporation,Qhicage, iii, a corpora-- tion oi Virginia Application December 13,1943, Serial f lo. 514,078

Our invention relates to controls for heating systems and moreparticularly to controls for heating systems the internal used onaircraft.

aircraft heating systems, it is common to provide an internal combustionheater supplied with combustion and ventilating air by a ram or ramslocated in a forward surfaceoi the aircombustlon type craft and sopositioned that movement of'the at a fixed rate to the aircraft heaterunder varying conditions of altitude and speed, it is desirable tosupply a uniform mass rate of combustion air under all speed andaltitude conditions of aircraft operation. r

An object of our invention is to provide a control for heating systemsof the foregoing type having means for supplying an -'approximatelyuniform mass rate of combustion air to the internal combustion heaterunder varying speed and altitude conditions.

Another object of our invention ls' to provide a new and improved valveto compensate for variations in speed and altitude.

Other objects and advantages will become apparent as the descriptionproceeds.

In the drawings:

Fig. l is a view showing a preferred embodiment of our invention andillustrating the heater and certain other parts in section;

Fig. 1A is a continuation of the righthand of Fi 1;

Fig. 2 is a transverse, sectional view taken on the line 2-2 of Fig. 1Aand shows details'of a thermostatically controlled ventilating airvalve;

Fig. 3 is a transverse, sectional view taken on theline 33 of Fig. 1Aand shows details of a support for the ventilating air valve;

Fig. 4 is a transverse, sectional view of the heat exchanger and istaken on the line 4-4 of Fig. 1;

end

. Fig. 5 is a transverse, sectional view taken on the line 5-5 of Fig. 1and shows an end view of the heat exchanger; I

Fig. 6 is a. transverse, sectional view through the compensating valveand is takenon the line 5 Elaims. U91. mil-did) In Fig. 1, we haveillustrated our invention as being applied to a heater indicatedgenerally by reference character it having a cylindrical casing l2 whoselefthand or inlet end is connected to a ventilating air supply pipe idin communication with a ventilating air ram it located in a forwardsurface it of an aircraft fuselage wing or other structural part. Theheater ltl has a combustion chamber 25 which discharges hot products oicombustion into the central gas passage 22 of a spiral heat exchanger26, which is illustrated as being of the type described and claimed inthe co-pending application of William C. Parrish, Serial No. 494,155,filed July 10, 1943. As most clearly shown in Fig. 4, the central gaspassage 22 communicates wth a spiral gas passage 26 leading to anexhaust outlet 28 connected to an exhaust pipe 30. 7

Ventilating air entering the ram 56 passes lengthwise of the ventilatingair pipe it and into the lefthand end of the heater casing it. This airflows about the combustion chamber 20 and absorbs some heat from thewalls thereof. The ventilating air then flows through the air passages32 in the heat exchanger 2% and absorbs plurality of outlets located'lnthe same or different spaces.

In Fig; 1A, we have illustrated a thermostatic ventilating air controlvalve 36 as being located in the duct 34'. This valve comprises astationary cone 38 mounted in a supporting spider d0 bolted or otherwiseattached to the wall of the duct M. A rotatable cone 62 is located inthe stationary cone 38 and is mounted on a shaft fit having one endsupported in a tubular extension 46 of the cone 3B. The other end of theshaft 84 is supported in a second spider 58. The shaft 44 is secured tothe fixed cone 3% as by means of solder 50, or in any other suitablemanner.

The rotatable cone s2 is mounted on a bearing member 52 rotatablycarried on. the shaft 5d and held against longitudinal displacement by acollar 54 secured to the shaft M by a set screw 55. A thermostat 5B inthe form of a bi-metallic strip spirally arranged has one end attachedby a screw to the rotatable cone t2 and the other end attached by ascrew 52 tothe shaft 64. Each of the cones is provided with rows ofholes which are brought into more or less registry It is, therefore,unnecessary to have the cones 36- and 38 closely fit each other and someslight space is preferably provided therebetween. This loose fit of thetwo cones simplifies production problems in manufacturing the valve andalso pre vents the valve from sticking if either of the cones shouldwarp slightly.

Fuel is injected into the combustion chamber in the form of a fine spraythrough a nozzle 64 which is supplied with fuel through a pipe 66connected with a source of fuel under constant pressure. A solenoidvalve 68 is located in the fuel supply pipe and cuts of! the supply offuel to the nozzle 64 when the master heater control switch for startingand stopping the heater is open. We also provide controls forautomatically closing this solenoid valve whenever insufficientventilating air is supplied by the ram I6 and whenever the ventilatingair in the duct 34 attains an unduly high temperature.

Referring to- Figs. 1, 1A and 8, it will be seen that the solenoid valve68 has one side grounded, as indicated at II, and the other sideconnected by conductor 12 to contact 14 of a Fenwall switch I6 locatedin the ventilating air duct 34. The other contact 18 of the switch 16 isconnected by conductor 80 to the terminal 82 of a switch 84 which iscontrolled by the pressure in the ventilating air supply pipe I4. Theother terminal 86 of the switch 84 is connected to the battery or othersource of current 88 through the master switch 10. The switch 84 iscontrolled by 9. diaphragm 80 whose lower side is exposed to atmosphericpressure and whose upper side is exposed to the pressure in a diaphragmchamber 82 which communicates with the ventilating air supply pipe I4through a nipple 94. The operation of this switch 84 is such that theswitch is normally open and closes only when the pressure in theventilating air supply pipe I4 is sumcient to afford the smallestdesirable flow of ventilating air for the heater I0.

The Fenwall switch I6 is set to remain closed except when theventilating air in the duct 34 attains an undesirably high temperature,which causes this switch to open and break the circuit to the solenoidvalve 68, thereby cutting off the supply of fuel to the nozzle 64. Assoon as the temperature of the air in the duct 34 drops appreciably, theFenwall switch I6 will again close and heater operation will be resumedif the manual control switch I0 and ventilating air responsive switch 84remain closed. From the foregoing, it is apparent that the supply offuel to the nozzle is controlled by three switches arranged in seriesand that the supply of fuel to the nozzle is cut off as soon as any oneof these switches opens.

The fuel delivered to the combustion chamber 20 by the nozzle 64 isdischarged substantially axially of a perforated sheet metal cone 96.Combustion air is supplied to the combustion chamber through combustionair pipe 98 connected to a combustion air ram I00 illustrated as locatedin the same surface I8 containing the ventilating air ram I6, althoughif desired these rams may be located in different parts of the airplanestructure. Part of the combustion air supplied to the combustion chamberflows through the perforations in the cone 86 to unite with the fuelspray and the remainder of the combustion air flows around the large endof this cone to mix with the fuel.

The mixture of fuel and air created in the combustion chamber isinitially ignited by an electrical igniter I02, which is disconnectedfrom its source of current after the heater attains normal operation.The control circuit for this igniter is best shown in Fig. 8. One sideof the electrical igniter I02 is grounded to the wall of the combustionchamber, as indicated at I03, whereas the Other side of this igniter isadapted to be connected by a relay I04 to the conductor leading to thebattery 88 through the main switch 10 and. ventilating air controlswitch 84. The circuit for energizing the relay I04 is controlled by asecond Fenwall switch I06 also located in the ventilating air duct 34and having one contact grounded, as indicated at I08. The Fenwall switchI06 is normally closed when the heater is not operating and remainsclosed after operation is initiated until the ventilating air in theduct 34 attains a predetermined temperature, whereupon this switch I06opens to break the relay circuit and thereby cut off the supplyofcurrent to the igniter- I02. The switch I06 remains in open positionas' long as the air in the duct 34 is at this predeter mined temperatureor any higher temperature.

The normal tendency of the rams I6 and I08.

is to increase the supply of ventilating air andcombustion air withincreases in aircraft speed.

The mass of the air supplied by these rams also varies with the altitudeat which the aircraft is operating, being less at high altitudes andgreater at low altitudes. The thermostatic ventilating air v valvelocated in the duct 34 prevents the ram This thermostatic valve alsotends to compensate for variations in ventilating air flow through theheater, due to opening or closing shutters controlling outletsconnecting the duct 34 with cabins or other spaces receiving ventilatingair.

An important feature of our invention lies in the provision of means forregulating the supply of combustion air to the combustion chamber toafford a substantially uniform mass of combustion air for all variationsin speed and altitude. This means comprises a speed and altitudecompensating valve IIO controlling communication between the combustionair supply pipe 68 and a bypass pipe II2 leading to the exhaust pipe 30,whereby excess of combustion air supplied by the ram I00 is dischargedinto the exhaust pipe 30 and does not enter the combustion chamber.

This combustion air control valve is best shown in Figs. 6 and '7 andcomprises a base H4 attached by screws II6 to a pipe section 98A forminga part of the combustion air supply pipe 98. The base II4 has an airinlet opening II8 communicating with a lateral opening I20 in the wallof pipe section 98A. The base II4 also provides a seat I22 for a sheetmetal valve I24 which is urged towards its seat by a spring I26.

The other end of the spring I26 rests against a washer i2 8 supported bya sheet metal nut I30 rotatable on a screw I32 having a reduced threadedextension I34 secured to the base of a cup shaped housing I36 enclosingthe valve member I24, spring I26, and associated parts. A housing IIO issecured to the base II4 by screws mm h m.

I, or in any other suitable manner. The nut I" has a scalloped edge I40normally engagedby a pin I42 to hold the nut I30 in adjusted position.

The pin I42 has an enlarged, threaded portion I44 secured in a ferruleI48 attached to the base the housing I36 and this end of the pin isprovided with an enlarged head having a screw driver ker! I48. Thetension of spring I25 may be adjusted by unscrewing pin I42 and usingthe smooth portion of this pin as a pry to rotate the nut I30 in thedesired direction, the threaded opening in the ferrule I46 beingsufliciently' bigger than the smooth end of the pin I42 to permit suchuse of this pin.

Altitude compensation for the valve member combustion air to saidheater, an exhaust pipe for discharging products ofcombustion from saidheater, means for supplying ventilating air to said heater, meansforming a bypass connecting said ram with said exhaust pipe, and a valveinterposed in said bypass and controlling air flow through said bypassto vary the mass of air flow member operable to supplement the pressureof I24 is provided by an evacuated sylphon I50, having one end formed bythe enlarged po'rtion I52 oi the screw I32. The other end of thissylphon is formed by a plate I54 having a threaded ex.-

said spring means upon decrease of ambient atmospheric pressure.

' 2. A heating system for aitcrattfcomprising an internal combustionheater, means for supplying a uniform flow of fuel thereto, a ram fortension I58 securedto the valve member I24 by ascrew I54.

The diiIerential pressure across the valve part I24 will increase withincreases in speed of the aircraft and decrease with decreases in speedof the aircraft. This is true both where the outlet end of the exhaustpipe is arranged to create.

a suction'in this pipev when the aircraft is in motion and when theoutlet end of this exhaust pipe is arranged to create no appreciablesuction in this pipe with motion of the aircraft. when the differentialpressure between the combustion air pipe "and exhaust pipe 30 issufilcient to deliver more than the desired quantity of combustion airto the combustion chamber, valve member I24 moves to increase itsopening in response to this pressure differential and permits the excessair delivered by the ram Hill to now through the bypass H2 directly intothe exhaust pipe so that approximately the desired amount of combustionair is delivered to the combustion chamber.

The degree of opening of the valve member I24 is thus varied by thevariations in differential pressure across this valve member so that theamount of air bypassed to the exhaust pipe fairly approximates, withinpermissible limits, theexwhich is inexpensive to manufacture and installand which insures safe and eilicient operation of the heating syfitemunder the widely varying consupplying combustion air to said heater, anexhaust pipe for discharging products of combustion from said heater,means for supplying ventilating air to said heater, a bypass connectingsaid ram with said exhaust pipe, valve means controlling air flowthrough said bypass in response to the ram pressure to vary the mass ofair flow to said combustion chamber with variations in speed of theaircraft, and means responsive to variations inambient atmosphericpressure for regulating said valve to compensate for altitude variationsand operative to increasingly resist the opening of said valve withincrease of altitude. 1

3. Apparatus of the class described, comprising an aircraft heaterhaving a combustion chamber,

means for supplying a uniform flow of fuel to said with increase ofaltitude.

4. Apparatus of the class described, comprising a heater having acombustion chamber, means for supplying fuel to said chamber. a ram forsupplying combustion air to said chamber, a pipe connecting said ramwith said chamber, means forming an escape outlet in said pipe, anexhaust pipe through which products of combustion from said combustionchamber are discharged to atditions encountered in aircrait'use. Whilewe" have illustrated and described in detail only a single embodiment orour invention, it is to be understood that our invention is not limitedto ,the particular details shown and described but may assume numerousother forms and that our invention includes all modifications,variations .and equivalents coming within the appended mosphere, a,valve controlling flow of air through said escape outlet, said valveincluding a valve member responsive to pressure diii'erentials betweensaid escape outlet and said ram, spring means urgin said valve membertoward closed position, and means forming an evacuated chamber having amovable wall connected to said valve member and operable to supplementthe load of the spring means upon decrease of ambient atmosphericpressure.

5. Apparatus of theclass described comprising an internal combustionheater, means 101' supplying ventilating air to said heater, a pipe forsupplying fuel to said heater, a pipe for supplying combustion air tosaid heater, a valve for cutting off fuel supply to said heater, meansresponsive to the pressure of the air supplied at the ventilating airinletof said heater for controlling sald valve. said last-named meansbeing independent of the pressure in said last-named pipe andfunctioning to open said valve when the pressure in said ventilating airsupply means is equal to .or above a, predetermined minimum, and meanslocated at said heater outlet and responsive directly to the temperatureof ventilating air flowing from the heater for controlling said valve.said last-named means being interconnected with and rendered operativeby said second-named means and functioning to cause closing of saidvalve when the temperature of the ventilating air REFERENCES CITED Thefollowing references are of record in the flle of this patent:

Number UNITED STATES PATENTS Name Date Gerdes Sept. 1, 1908 StephensJune 8, 1920 Strong Nov. 24, 1925 Thurm June 24, 1930 Evers et a1 Oct.21, 1940 Martin Dec. 8, 1931 Buck July 25, 1933 Anxionnaz Mar. 29, 1938Myler Nov. 22, 1938 McGrath Feb. 6, 1940 Matthes Apr. 16, 1940 HolthouseJune 16, 1942 Jacobsson Mar. 9, 1943 Hess et a1 Mar. 16, 1943 McCollumDec. 5, 1944 Arnhym Apr. 8, 1947

